Iodine quantification to characterize primary lesions, metastatic and non-metastatic lymph nodes in lung cancers by dual energy computed tomography: An initial experience

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Abstract

Purpose

To investigate whether dual energy computed tomography (CT) with iodine quantification can characterize primary lesions and metastatic lymph nodes from non-metastatic ones in non-small cell lung cancer (NSCLC).

Materials and methods

Sixty-one patients with NSCLC confirmed by pathology underwent chest contrast CT scan with dual energy computed tomography before surgery. The Iodine concentration (IC) and normalized iodine concentration (NIC) values of the primary lesions, 20 metastatic and 20 non-metastatic lymph nodes were measured, respectively. The differences between the primary lesions, metastatic and non-metastatic lymph nodes were statistically analyzed.

Results

For the IC and NIC values of the primary lesions and their metastatic lymph nodes, there were no significant differences between lung squamous cell carcinomas and adenocarcinomas, respectively (P > 0.05), while significant differences existed between metastatic and non-metastatic lymph nodes, respectively (P < 0.05). The IC of 29.32 100 μg/cm3 and NIC value of 0.4328 of a lymph node represented the optimal threshold to discriminate metastatic from non-metastatic lymph nodes and yielded the following: sensitivity, 80% and 75%; specificity, 65% and 75%; PPV, 70% and 75%; NPV, 76% and 75%; accuracy, 73% and 75%, respectively.

Conclusion

Although its value in distinguishing primary lesions and their metastatic lymph nodes in NSCLC needs to be verified in further studies, dual energy CT with iodine quantification may be used to differentiate metastatic from non-metastatic lymph nodes in NSCLC.

Introduction

Lung cancer is the most common cancer in both men and women, and is also the leading cause of cancer death throughout the world. Non-small cell lung cancer (NSCLC) accounts for 85–90% of all lung cancer. Adenocarcinoma and squamous carcinoma are the main histological subtypes of NSCLC. The benefits of oncology treatment including chemotherapy, radiotherapy and targeted therapy rely on the tumor’s histologic type, stage and molecular markers. Therefore, initial staging of disease extent is important in patients with newly diagnosed NSCLC, in order to select the most appropriate therapeutic option and to derive prognostic information.

Because of advanced stage and/or comorbidities at presentation, most lung cancers are nonresectable. It is therefore advantageous to diagnose and stage the patient’s tumor with small biopsies or cytologic examination rather than with surgical resection specimens. However, some patients cannot be performed the biopsies due to the tumor location or other reasons. Furthermore, staging of lung cancer including the analysis of the lymph nodes is second in importance only to the pathologic determination of cell type. Accurate staging provides prognostic information and stage determines treatment strategies for all types of lung cancer. Imaging is playing an important role in discrimination both subtypes of NSCLC and tumor staging. In the past decades, computed tomography (CT) has been employed as a main imaging modality for NSCLC diagnosis and staging [1]. Morphologic assessment of tumor has been the mainstay of conventional CT imaging evaluation in clinical practice. Recently, a new dual-energy CT technique based on the switching between high- and low-energy data sets from view to view is introduced. This technique enables registration of data sets for creation of material-decomposition images (e.g., water- and iodine-based material-decomposition images) for quantitative iodine measurement. The CT scanning method has been added and demonstrated its benefits in clinical applications such as differentiating metastatic from non-metastatic lymph nodes in rectal cancer, clear cell from papillary renal cell carcinoma and benign from malignant solitary pulmonary nodule [2], [3], [4].

However, to the best of our knowledge, there are few studies about the value of dual energy CT with iodine quantification in the differentiation and staging of NSCLC. It is possible for post-contrast dual energy CT imaging technology to determine and quantify iodine-related attenuation with the assumption of a correlation with perfusion parameters and the degree of malignant tissue vascularization. The aim of our study was to investigate whether dual energy CT with iodine quantification could characterize primary lesions and their metastatic lymph nodes between lung adenocarcinomas and squamous carcinomas, and discriminate metastatic lymph nodes from non-metastatic ones.

Section snippets

Patients

This retrospective study was approved by our institutional review board for human research and thus written informed consent was obtained from all patients. From January 2012 to December 2014, seventy-one patients suspected of primary peripheral lung cancer appearing as nodules or masses on the non-enhanced CT images underwent enhanced chest dual energy CT scanning before operation. All pulmonary lesions and lymph nodes were subsequently confirmed by surgical resection. Of the 71 patients, we

Results

The patients in the present analysis were divided into 27 patients with squamous cell carcinomas and 34 patients with adenocarcinomas, all of them were peripheral non-small cell lung cancer. The inter-observer agreement between the two readers in the measurements was excellent. The ICC for the IC and NIC measurements in primary lesions was 0.83 and 0.86, respectively. The ICC for the IC and NIC measurements in lymph nodes was 0.94 and 0.93, respectively. The mean IC and mean NIC of primary

Discussion

It is well known that CT imaging is playing an important role in the diagnosis, differentiation and staging of lung cancer. However, our research results indicate that dual energy CT with iodine quantification has a limited value in distinguishing primary lesions in NSCLC and metastatic lymph nodes between lung squamous cell carcinomas and adenocarcinomas, but may be useful in differentiating metastatic from non-metastatic lymph nodes.

Recent studies have demonstrated that quantification of

Conflict of interest

All authors have no conflicts to disclose.

Acknowledgments

This study was supported by a grant from Natural Science Foundation of China (Grant no. 81201138). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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